package ly.jobdu;

import java.util.Scanner;

public class Q1047Prime {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int a = 0;
        while(scanner.hasNext()) {
            a = scanner.nextInt();
            isPrime(a);
        }
    }
     
    public static void isPrime(int n) {
        if(n <= 1) {
            System.out.println("no");
        } else {
            String result = "yes";
            for(int i = 2; i <= Math.sqrt(n); i++) {
                if(n % i == 0) {
                    result = "no";
                    break;
                }
            }
            System.out.println(result);
        }
    }
}
